Re: [Xen-devel] [PATCH 34/34] RFC x86: introduce directio virt cap

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Aug 21, 2018 at 11:25:58AM +0100, Wei Liu wrote:
> On Tue, Aug 21, 2018 at 10:32:18AM +0200, Roger Pau Monné wrote:
> > On Fri, Aug 17, 2018 at 04:12:52PM +0100, Wei Liu wrote:
> > > hvm_directio is set when iommu is enabled, but in fact iommu is not
> > > tied to HVM. In order to not break existing tools, expose a new flag
> > > directio for (iommu_enabled && !hvm_enabled).
> > > 
> > > RFC This doesn't build at the moment. Do we care about that flag being
> > > inaccurate?
> > 
> > I think there is no hardware out there with an IOMMU that don't have
> > virtualization extensions (ie: having VTd but not VTx for example),
> > but maybe I'm wrong.
> 
> The question is whether it makes sense to expose the name "hvm_directio"
> at all when you can't run an HVM guest in the first place.
> 
> Also iommu isn't an HVM only feature, PV guests can also make use of it
> if I understand correctly, hence the suggestion of "directio".

Right, I see your point.

Could we remove this hvm_directio artifact and just expose an iommu
capability?

Since this is a sysctl I think we can change the interface without
issues, so I would just
s/XEN_SYSCTL_PHYSCAP_hvm_directio/XEN_SYSCTL_PHYSCAP_iommu/.

Roger.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel